Oxytocin and its role in caloric intake and appetite: A preregistered living systematic review and meta-analysis

Oxytocin is a hypothalamic hormone and neuromodulator that has been linked to a variety of different functions, including parturition, social behavior, and cognitive processing. More recently, oxytocin has also been associated with metabolism and energy balance. However, evidence to date in this field has been inconsistent, especially in human research. To address this, we performed a preregistered systematic review and meta-analysis, which synthesized existing literature on the effect of exogenous oxytocin administration compared to a placebo on caloric intake and appetite in humans, using a living meta-analysis approach. Results indicated a significant, reductive effect of oxytocin administration on appetite in participants belonging to certain patient groups (e.g., obesity or type II diabetes; Hedges' g = -0.21). A separate moderator analysis evaluating oxytocin's effect on caloric intake revealed a conditional effect depending on the patient group, with the obesity group showing a significant effect. We did not find any statistically significant effects in healthy participants. However, further analyses revealed that these effects were also not equivalent, indicating that the data are currently too insensitive to draw clear conclusions. Taken together, the results provide some evidence for the role of oxytocin in regulating appetite in an anorexigenic, possibly homeostatic fashion. Future updates in this living meta-analysis may lead to more definitive conclusions.